Sintered capacitor electrode including a folded connection

ABSTRACT

This document discusses capacitive elements including a first, second and third electrode arranged in a stack. The third electrode is positioned between the first and second electrode. An interconnect includes a unitary substrate shared with the first and second electrodes. The interconnect is adapted to deform to accommodate the stacked nature of the first and second electrodes. The unitary substrate includes a sintered material disposed thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/968,555, issued as U.S. Pat. No. ______, entitled “Sintered CapacitorElectrode Including a Folded Connection,” filed Dec. 15, 2010, whichclaims the benefit of U.S. Provisional Application No. 61/288,076, filedon Dec. 18, 2009, under 35 U.S.C. §119(e), each of which is incorporatedherein by reference in their entirety.

TECHNICAL FIELD

This document relates generally to energy storage and particularly tosintered electrodes to store energy in an implantable medical device.

BACKGROUND

Electrical stimulation therapy has been found to benefit some patients.For example, some patients suffer from an irregular heartbeat orarrhythmia and may benefit from application of electrical stimulation tothe heart. Some patients suffer from a particular type of arrhythmiacalled a fibrillation. Fibrillations may affect different regions of theheart, such as the atria or the ventricles. When a fibrillation occursin the ventricles, the heart's ability to pump blood is dramaticallyreduced, putting the patient at risk of harm. It has been found thatapplying an electrical stimulation to the patient can effectively treatpatients suffering from disorders such as from fibrillation by restoringa regular heartbeat.

Because disorders such as fibrillations can happen at any time, it ishelpful to have a device that is easily accessible to treat them. Insome cases, it is helpful if that device is portable or implantable. Indeveloping a device that is portable or implantable, it is helpful tohave access to subcomponents that are compact and lightweight and thatcan perform to desired specifications.

SUMMARY

This document provides apparatus related to energy storage deviceshaving folded portions to couple electrodes of the devices. Oneapparatus embodiment includes a hermetically sealed capacitor casesealed to retain electrolyte, a first electrode disposed in thecapacitor case, a second electrode disposed in the capacitor case in astack with the first electrode, the second electrode including sinteredmaterial disposed on a flexible unitary substrate, with the flexibleunitary substrate included a connection portion that is flexed andcoupled to the first electrode. The apparatus includes, a thirdelectrode disposed in the capacitor case in the stack, a first terminalcoupled to the first electrode, and a second terminal coupled to thethird electrode, the second terminal electrically isolated from thefirst terminal.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive treatmentof the present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Otheraspects of the invention will be apparent to persons skilled in the artupon reading and understanding the following detailed description andviewing the drawings that form a part thereof. The scope of the presentinvention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate generally, by way of example, variousembodiments discussed in the present document. The drawings are forillustrative purposes only and may not be to scale.

FIG. 1 is a schematic of a medical system including a sinteredcapacitor, according to some embodiments.

FIG. 2 is an implanted medical system including a sintered capacitor,according to some embodiments.

FIG. 3 shows a capacitor according to some embodiments of the presentsubject matter.

FIG. 4A shows an isometric view of a capacitor element according to someembodiments of the present subject matter.

FIG. 4B shows an isometric view of a capacitor element according to someembodiments of the present subject matter.

FIG. 5 shows a side view of a capacitor element according to someembodiments of the present subject matter.

FIG. 6 shows a side view of a capacitor element according to someembodiments of the present subject matter.

FIG. 7 shows a side view of a capacitor element according to someembodiments of the present subject matter.

FIGS. 8A and 8B show side views of a capacitor element according to someembodiments of the present subject matter.

FIG. 9 shows a capacitor element according to some embodiments of thepresent subject matter.

FIGS. 10A and 10B show a capacitor element according to some embodimentsof the present subject matter.

FIG. 11 shows a side view of a capacitor element according to someembodiments of the present subject matter.

DETAILED DESCRIPTION

The following detailed description of the present invention refers tosubject matter in the accompanying drawings which show, by way ofillustration, specific aspects and embodiments in which the presentsubject matter may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresent subject matter. References to “an”, “one”, or “various”embodiments in this disclosure are not necessarily to the sameembodiment, and such references contemplate more than one embodiment.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope is defined only by the appended claims,along with the full scope of legal equivalents to which such claims areentitled.

This document concerns sintered electrodes for use in an electricalenergy storage device. Specific examples include sintered anodes formedof aluminum or its alloys. Certain examples are for use in aluminumelectrolytic capacitors. Examples include electrodes with a sinteredportion disposed onto at least one side of a substrate. Some examplesinclude a stack of electrodes in which the substrates of multipleelectrodes are interconnected. This interconnection method improves uponenergy storage devices using etched electrodes because the foils may bebent together for interconnection with a low risk of breakage, whereasetched materials often break. Additional benefits stem from an increasedsurface area that is a product of sintering.

Sintering results in many interstices (i.e., spaces) between grains ofthe electrode. Sintered electrodes resemble crushed grains withinterstices between the grains. The interstices are filled withelectrolyte, thereby increasing capacitance per unit of volume, ascapacitance is proportional to a surface area exposed to electrolyte. Anelectrode with such interstices offers improved lateral or parallelmovement of electrons in relation to a major surface of a flat electrodelayer, as etched electrodes restrict lateral movement because theetchings result in voids that are typically perpendicular to the majorsurface of the flat layer. Accordingly, some examples have a lower ESR(equivalent series resistance) compared to etched foils due to thisenhance ionic flow.

Overall, an energy storage device using the sintered electrodesdescribed here is well suited for use in an implantable medical devicesuch as a defibrillator. Because sintering can produce a variety ofshapes, sintered electrodes can be used to create energy storage devicessuch as capacitors that have custom shapes versus simple cylinders or aprism having a parallelogram as its base. In some examples,manufacturing efficiency is improved, such as by allowing electrodes tobe nested on a web before they are excised from the web and stacked intoa capacitor. In other words, nesting reduces waste by allowing more ofthe web to be converted into electrodes. The interstices are very small,making the electrodes rigid and able to withstand handling by a machineor assembly personnel. These electrodes demonstrate an improved energydensity over etched electrodes and are therefore useful to make smallerimplantable devices that are able to deliver an amount of energy for aparticular therapy.

FIG. 1 is a schematic of a medical system 100 including a sinteredcapacitor, according to some embodiments. The medical system 100represents any number of systems to provide therapeutic stimulus, suchas to a heart. Examples of medical systems include, but are not limitedto, implantable pacemakers, implantable defibrillators, implantablenerve stimulation devices and devices that provide stimulation fromoutside the body, including, but not limited to, externaldefibrillators.

Electronics 104 are to monitor the patient, such as by monitoring asensor 105, and to monitor and control activity within the system 100.In some examples, the electronics 104 are to monitor a patient, diagnosea condition to be treated such as an arrhythmia, and control delivery ofa stimulation pulse of energy to the patient. The electronics 104 can bepowered wirelessly using an inductor. Alternatively, the electronics 104can be powered by a battery 106. In some examples, electronics 104 areto direct small therapeutic bursts of energy to a patient from thebattery 106.

For therapies, such as defibrillation, that use energy discharge ratesexceeding what battery 106 is able to provide, a capacitor 108 is used.Energy from the battery 106 is controlled by the electronics 104 tocharge the capacitor 108. The capacitor 108 is controlled by theelectronics 104 to discharge to a patient to treat the patient. In someexamples, the capacitor 108 completely discharges to a patient, and inadditional examples, the capacitor is switched on to provide therapeuticenergy and switched off to truncate therapy delivery.

Some examples of a medical system 100 include an optional lead system101. In certain instances, after implantation, the lead system 101 or aportion of the lead system 101 is in electrical communication withtissue to be stimulated. For example, some configurations of lead system101 contact tissue with a stimulation electrode 102. The lead system 101couples to other portions of the system 100 via a connection in a header103. Examples of the lead system 101 use different numbers ofstimulation electrodes and/or sensors in accordance with the needs ofthe therapy to be performed.

Additional examples function without a lead 101. Leadless examples canbe positioned in contact with the tissue to be stimulated, or can bepositioned proximal to tissue to shock the tissue to be stimulatedthrough intermediary tissue. Leadless examples can be easier to implantand can be less expensive as they do not require the additional leadcomponents. The housing 110 can be used as an electrode in leadlessconfigurations.

In certain embodiments, the electronics 104 include an electroniccardiac rhythm management circuit coupled to the battery 106 and thecapacitor 108 to discharge the capacitor 108 to provide a therapeuticdefibrillation pulse. In some examples, the system 100 includes an anodeand a cathode sized to deliver a defibrillation pulse of at leastapproximately 50 joules. Other configurations can deliver larger amountsof energy. Some configurations deliver less energy. In some examples,the energy level is predetermined to achieve a delivered energy levelmandated by a governing body or standard associated with a geographicregion, such as a European country. In an additional embodiment, theanode and cathode are sized to deliver a defibrillation pulse of atleast approximately 60 joules. In some examples, this is the energylevel is predetermined to achieve an energy level mandated by agoverning body of another region, such as the United States. In someexamples, electronics 104 are to control discharge of a defibrillationpulse so that the medical system 100 delivers only the energy mandatedby the region in which the system 100 is used. In some examples, a pulseof 36 joules is delivered.

Packaging anodes and cathodes can reduce their efficiency.Interconnections between conductors coupled to electronics and to theelectrodes of the capacitor 108 decrease efficiency, for example.Accordingly, anodes and cathodes are sized to compensate for decreasesin efficiency. As such, in some embodiments, the capacitor 108 includesanodes and cathodes sized and packaged to deliver a defibrillation pulseof at least approximately 50 joules. Some are sized and packaged todeliver a defibrillation pulse of at least approximately 60 joules.

One characteristic of some sintered electrode examples is that at leastone anode and a cathode have a DC capacitance that is approximately 23%greater than a AC capacitance for the at least one anode and the cathodeof an etched capacitor that has 74.5 microfarads per cubic centimeter.In some examples, the at least one anode and the cathode have an ACcapacitance of at least 96.7 microfarads per cubic centimeter at 445total voltage. In some examples, this is comparable to an operatingvoltage of about 415 volts. This is a 30% improvement over an etchedcapacitor that has 74.5 microfarads per cubic centimeter. Total voltageis the voltage that allows 1 milliamp of leakage per square centimeter.Some examples are aged to 415 volts.

In certain examples, the capacitor 108 includes a capacitor case 112sealed to retain electrolyte. In some examples, the capacitor case 112is welded. In some instances, the capacitor case 112 is hermeticallysealed. In additional examples, the capacitor case 112 is sealed toretain electrolyte, but is sealed with a seal to allow flow of othermatter, such as gaseous diatomic hydrogen or a helium molecule. Some ofthese examples use an epoxy seal. Several materials can be used to formcase 112, including, but not limited to, aluminum, titanium, stainlesssteel, nickel, a polymeric material, or combinations of these materials.The case 112 is sealed to retain electrolyte. Various electrolytes canbe used including, but not limited to, Suzuki-Techno Corporationelectrolyte model 1184. The case 112 includes a seal, such as a resinbased seal including but not limited to epoxy, in some examples. Someexamples include a rubber seal to seal case portions to one another, orto seal subcomponents such as a feedthrough to one or more case portion.In some examples, case 112 is welded together from subcomponents. Someexamples include a case that includes one or more backfill ports, butthe present subject matter is not so limited.

A hermetically sealed device housing 110 is used to house components,such as the battery 106, the electronics 104, and the capacitor 108.Hermeticity is provided by welding components into the hermeticallysealed device housing 110, in some examples. Other examples bondportions of the housing 110 together with an adhesive such as a resinbased adhesive such as epoxy. Accordingly, some examples of the housing110 include an epoxy sealed seam or port. Several materials can be usedto form housing 110, including, but not limited to, titanium, stainlesssteel, nickel, a polymeric material, or combinations of these materials.In various examples, the housing 110 and the case 112 are biocompatible.

The capacitor 108 is improved by the present electrode technology inpart because it can be made smaller and with less expense. Theimprovement provided by these electrodes is pertinent to any applicationwhere high-energy, high-voltage, or space-efficient capacitors aredesirable, including, but not limited to, capacitors used forphotographic flash equipment. The present subject matter extends toenergy storage devices that benefit from high surface area sinteredelectrodes including, but not limited to, aluminum. The electrodesdescribed here can be incorporated into cylindrical capacitors that arewound, in addition to stacked capacitors.

FIG. 2 is an implanted medical system 200, implanted in a patient 201,and including a sintered capacitor, according to some embodiments. Thesystem includes a cardiac rhythm management device 202 coupled to afirst lead 204 to extend through the heart 206 to the right ventricle208 to stimulate at least the right ventricle 208. The system alsoincludes a second lead 210 to extend through the heart 206 to the leftventricle 212. In various embodiments, one or both of the first lead 204and the second lead 210 include electrodes to sense intrinsic heartsignals and to stimulate the heart. The first lead 204 is in directcontact (e.g., touching) with the right atrium 214 and the rightventricle 208 to sense and/or stimulate both those tissue regions. Thesecond lead 210 is in direct contact with the left atrium 216 and theleft ventricle 212 to sense and/or stimulate both those tissue regions.The cardiac rhythm management device 202 uses the lead electrodes todeliver energy to the heart, either between electrodes on the leads orbetween one or more lead electrodes and the cardiac rhythm managementdevice 202. In some examples, the cardiac rhythm management device 202is programmable and wirelessly communicates 218 programming informationwith a programmer 220. In some examples, the programmer 220 wirelessly218 charges an energy storage device of the cardiac rhythm managementdevice 202.

FIG. 3 shows a capacitor 308 according to some embodiments of thepresent subject matter. In some examples, the capacitor 308 is flat.Various embodiments include a plurality of electrode layers. Someexamples include a plurality of electrodes aligned in a stack. Althoughthe illustrated capacitor is “D” shaped, in other embodiments, thecapacitor is shaped differently, including but not limited to,rectangular, circular, oval, square or other symmetrical or asymmetricalshapes. In various embodiments, a stack defines a customthree-dimensional form factor shaped to conform to an interior volume ofa case such as a capacitor case. In some embodiments, the capacitor case312 is made from conductive material such as aluminum. In otherembodiments, the case 312 is made from non-conductive material such asceramic or plastic.

In some examples, the capacitor 308 includes a first terminal 322 and asecond terminal 323 to connect the capacitor stack 321 to an electricalcomponent, such as an electrical component included in an implantablemedical device. In some embodiments, a first terminal 322 is afeedthrough terminal insulated from the case, while the second terminal323 is directly connected to the case. Other embodiments may incorporateother connection methods including, but not limited to, a differentnumber of terminations and a different number of feedthroughs. Incertain examples, the capacitor stack 321 includes one or more capacitorelements such as elements discussed here.

FIG. 4A and 4B show an isometric view of a capacitor element 430according to some embodiments of the present subject matter. One or morecapacitor elements may be used in forming a capacitor stack. A capacitorelement 430 includes a first electrode layer 431, separator material 432proximate the first electrode layer, and a second electrode 433. Thesecond electrode includes a second electrode layer substrate 434, athird electrode layer substrate 435 and a folded portion 436 couplingthe second electrode layer substrate 434 and the third electrode layersubstrate 435. The folded portion 436 folded upon itself to couple thesubstrates 434, 435 in the stacked configuration. In some examples, thesecond and third electrode layers 438 a, 438 b include sintered material439 disposed on a substrate that is unsintered. In various embodiments,the substrate includes aluminum. In various embodiments, the sinteredportion includes aluminum. The folded portion 436, in some embodiments,includes sintered material. In other embodiments, the folded portionincludes one or more areas that are substantially free of sintering.

In some embodiments, the second electrode includes sintered material onone major surface 457 of the substrate. In various embodiments, thesecond electrode includes sintered material on both major surfaces 457,459 of the substrate (see FIG. 4B). In various embodiments, the layersof the second electrode of a capacitor element are stacked such thatperimeters of the substrate of each layer are substantially coextensive.In capacitors that may be made to fit a custom volume, the stackedelectrodes may be offset to provide the desired shape. Some examplesinclude a substantial overlap between adjacent electrodes.

In various embodiments, a layer may include a substantially sinter-freeportion for connecting to other electrical components including othercapacitor elements or other electrodes or electrode layers within thesame capacitor element.

FIG. 4B shows a capacitor element 480 with a sintered electrodesubstrate and an interconnect according to some embodiments of thepresent subject matter. In some embodiments, components of the capacitorelement, such as the first electrode layer 431 and the separatormaterial 432, may be notched 448 to allow for connection to an adjacentelement, other electronics or other capacitor elements. Such a notch 448allows a connecting member 445 to be coupled to a target componentwithout creating a bulge in components stacked onto the targetcomponent.

The illustrated embodiment of FIG. 4B shows a first electrode layer 431and separator material 432 between a second electrode layer 438 a and athird electrode layer 438 b. The first electrode layer 431 and separatormaterials 432 include a notch 448 to accommodate connecting memberscoupled to the second 438 a and third 438 b electrode layers withoutcreating a bulge in the stacked capacitor element 480. The secondelectrode layer illustrates a sinter-free area 449 for accommodating aconnecting member to couple to the substrate of the second electrodelayer 438 a. The third electrode layer 438 b shows a connecting member445, such as a first clip, coupled to a sinter-free area of the thirdelectrode layer 438 b. Various embodiments include a second clip coupledto the first electrode layer. In such embodiments the first and secondclips may be coupled together to interconnect the electrode layers. Theclips may be coupled together, for example, using a weld. Other forms ofcoupling connecting members together are possible without departing fromthe scope of the present subject matter including, but not limited to,laser welding, ultrasonic welding, using conductive adhesive orcombinations thereof. In various embodiments, the first electrode layeris a cathode and the second and third electrode layers include a firstand second anode plate. In some embodiments, a slotted interconnect maybe used to couple sinter-free portions of two or more electrode layerstogether. In various embodiments, an electrode includes a tab extendingfrom the perimeter of the substrate of the electrode. In someembodiments, more than one tab may extend from the perimeter of thesubstrate of an electrode.

In various embodiments, a capacitor stack may include many tabs. Thetabs may include various alignment arrangements to provide for variousconnections to capacitor terminations. In some embodiments, the tabs maybe aligned vertically to allow for efficient interconnection of thecorresponding capacitor electrodes. In some embodiments, some tabs maybe aligned but offset from other aligned tabs to allow for separateinterconnection such as for a partitioned capacitor. In variousembodiments, tabs of varying width may be used. Tabs of varying widthmay be stacked such that a first tab fully overlaps a wider adjacenttab. Such an arrangement allows for efficient connection of adjacenttabs such as by using a cold weld. Additionally, such an arrangementforms a more rigid composite connection tab as additional wider tabs arestacked together.

FIG. 5 shows a side view of a capacitor element according to someembodiments of the present subject matter. The capacitor element 530includes a number of cathode stacks 537 and a number of anode plates538. Adjacent anode plates 538 are connected by a folding portion 536,according to some examples. Each anode plate includes a sintered portion539 disposed on a substrate 540. In various embodiments, the substrateis a continuous, monolithic, solid, unitary piece of substrate materialthat forms a number of anode plates and folding portions of thecapacitor element. In some embodiments, the substrate is a foil. In someexamples, the substrate is an aluminum foil. Aluminum foil has athickness of less than 0.008 inches/0.2 mm in various examples. Somealuminum foils are less than or equal to 0.005 inches thick. These foilsare easily bent by hand and are easily torn by hand. Substrates that arethicker are additionally possible.

In some embodiments, the folding portion 536 connecting the anode plates538 is separate from one or both of the anode plates it couples. In suchembodiments, the folding portion 536 is coupled to an anode plate, forexample using a weld, such as a cold weld, a laser weld or an ultrasonicweld or other coupling method. In some embodiments, the folding portionis coupled to a sinter free portion of the anode plate substrate. Invarious embodiments, one or more anode plates include sintered materialdisposed on both sides of the substrate. The cathode stack 537 includesa cathode. In various embodiments, the cathode stack 537 also includesseparator material, such as separator material with absorbed or embeddedelectrolyte material.

FIG. 6 shows a side view of a capacitor element according to someembodiments of the present subject matter. The capacitor element 630includes a number of cathode stacks 637, anode plates 638, foldedportions 636 coupling anode plates, and anode tabs 641 coupled to theanode plates 638. In the illustrated embodiment, a number of anode tabs641 are gathered and welded 642 for connection to electronics, such aselectronics related to an implantable medical device. In someembodiments, one or more tabs are coupled to a case of capacitor 643.

The anode plates 638 include a sintered portion 639 disposed on asubstrate 640, such as an aluminum substrate in some examples. Invarious embodiments, the anode tabs 641 are extensions of the substrate640. In some embodiments, the anode tabs 641 are couple to thesubstrate, for example, the anode tabs may be coupled to the substrateof the anode plates at substantially sintering free portions of thesubstrate. In some embodiments, the tabs include sintered materialdisposed on a substrate.

FIG. 7 shows a side view of a capacitor element according to someembodiments of the present subject matter. The capacitor element 730includes a number of cathode stacks 737, a number of anode plates 738, anumber of folded portions 736 coupling anode plates, a number of foldingportions 744 coupling cathode stacks and a number of tabs 741 forelectrically coupling the anode plates 738 to each other using a clip745. The clip 745 may be used to couple to other electronics, such aselectronics related to an implantable medical device. In someembodiments, the clip 745 is coupled to a conductive case. In someembodiments, the clip 745 is coupled to a feedthrough of a case, wherethe feedthrough insulates the clip from the case. The cathode stackincludes a cathode electrode, and may include separator material, suchas separator material with absorbed or imbedded electrolyte material.The anode plates include sintered material 739 disposed on at least onemajor surface of an anode plate substrate 740. In various embodiments,sintered material is disposed on both major surfaces of an anode platesubstrate. In various embodiments, the folded portions connecting theanode plates and the folded portions connecting the cathode stacks arecontinuous portions of the respective substrates of the anode plates andcathode stacks. Such an arrangement may provide efficiencies related tomaterial and/or processing as each substrate can be excised from acontinuous web of substrate material. It is understood that although theillustrated embodiment shows subsequent folding portions extending fromopposite sides of the corresponding anode or cathode structure, otherorientation arrangements are possible, as are other anode and cathodesubstrate shapes, without departing from the scope of the presentsubject matter.

FIGS. 8A and 8B show side views of a capacitor element according to someembodiments of the present subject matter. The capacitor elements 830include a number of cathode stacks 837, a number of anode plates 838, anumber of folded portions 836 coupling anode plates, a number of tabs841 each coupled to an anode plate, and a clip 845 coupled to each anodetab 841 for electrically coupling the anode plates 838 to each otherand, in various embodiments, to other electrical components. Each anodeplate 838 includes a sintered material 839 disposed on a substrate 840.The anode plates 838 include sintered material 839 disposed on at leastone major surface of an anode plate substrate 840. In variousembodiments, sintered material 839 is disposed on both major surfaces ofan anode plate substrate 840. In various embodiments, the foldedportions 836 connecting the anode plates are continuous portions of theanode plate substrate 840. It is understood that although theillustrated embodiment shows subsequent folding portions extending fromopposite sides of the anode plate structure, other orientationarrangements and are possible, as are other anode substrate shapes,without departing from the scope of the present subject matter. Theanode tabs 841 may be a continuous piece of the substrate materialextending from the perimeter of the anode plate substrate 840. Invarious embodiments, the tabs 841 may be separate pieces of materialcoupled to the anode plate, for example, a tab may be coupled to asubstantially sintering free portion of the anode plate substrate. Theclips 845 coupled to the tabs are welded together to electrically couplethe anode plates. In the illustrated embodiment, the clips are coupledto a case 843 enclosing the capacitor element. The clips 845 are coupledto the case 843 using a conductive ribbon 846. In some embodiments, theclips 845 are coupled to a feedthrough 847 of the case 843 using aconductive ribbon 846, as is shown in FIG. 8B.

FIG. 9 shows a capacitor element according to some embodiments of thepresent subject matter. The capacitor element 930 includes a number ofcathode stacks 937, a number of anode plates 938 and folded portions 936connecting the anode plates. The folded portion 941 of an anode plateinterconnects each subsequent anode plate. A ribbon of conductivematerial 946 is used to interconnect the anode plates using the foldedportions. The ribbon of conductive material 946 is coupled to afeedthrough 947 of a case 943 for connection to other electronics, suchas electronics related to an implantable medical device. In variousembodiments, the conductive material 946, such as a ribbon, may be usedto couple the anode plates to the case. In some embodiments, the ribboninterconnects anodes of a single capacitor element. In some embodiments,the ribbon interconnects multiple capacitive elements, for example,using the folded portions of anode plates of each element. In variousembodiments, a ribbon is used to interconnect the anode plates 938 and atab is used to connect the interconnected anode plates to the case or toa feedthrough of the case. In various embodiments, folded portions ofthe anode plates may be arranged such that additional conductive ribbonsmay be used to interconnect the anode plates. In some embodiments, thefolded portions of the capacitor element, or multiple capacitorelements, are grouped at an offset to allow for partitioning of thecapacitor.

FIGS. 10A and 10B show a capacitor element according to some embodimentsof the present subject matter. FIG. 10A shows a partially assembledstack of capacitor components including sintered anode plates 1038 andcathode stacks 1037. Each anode plate and each cathode stack include anotch 1050 with an L-shaped tab extending from an interior side of thenotch. When stacked, the legs of the L-shaped tabs of the anode platesoverlap the legs of the L-shaped tabs of the cathode stacks. However,the L-shaped protrusions of the anode plates extend from the anode plateat the opposite end of the leg than do the L-shaped tabs extending fromthe cathode stacks. Once stacked, the legs of the L-shaped protrusionsof the anode plates and the cathode stacks are coupled, such as bywelding, to form a solid coupling of the tab legs. The middle section ofthe legs are then excised, such as by laser cutting, mechanical etching,chemical etching or grinding, for example. FIG. 10B shows the structureafter the legs of the tabs have been excised. Excising the middle of thelegs results in a pair of connected tabs 1051, 1052 forming somewhatrigid connections. A first set of connected tabs 1051 couples the anodeplates together, and a second set of connected tabs 1052 couples thecathode stacks together. The above method of forming anode and cathodeconnection tabs uses materials of the initial anode and cathodestructures to form the isolated tabs. The resulting tabs form a rigidstack when welded together. Such tabs provide robust connection pointsfor additional electronics and reduce the risk of damaging the cathodesubstrate, for example, when handling the capacitor element duringprocessing. Such substrates are often very thin and easily damagedduring processing.

FIG. 11 shows side view of a capacitor element according to someembodiments of the present subject matter. The capacitor element 1130includes a number of cathode stacks 1137, a number of sintered anodeplates 1138, and a number of folded portions 1136 coupling anode platesstacked with the cathode stacks. Several of the anode plates include atab 1153 extending from the anode plate. The tabs are rolled from adistal end back toward the anode plate from which each extends. Thediameter of the rolled portion 1154 is approximately equal to thespacing of adjacent anode plates. The rolled portion 1154 of the tabsreduce stress on the tabs that may otherwise exist when connecting thetabs without the rolled portion. In various embodiments, the rolledportion 1154 of the tabs are coupled together, for example with a weld,to form an anode connection. In various embodiments, the tabs are formedfrom substrate material 1140 of the anode plate on which sinteredmaterial 1139 is disposed. In various embodiments, the rolled portion1154 of the tabs in used to interconnect the anode plates and anunrolled tab 1141 is used for connecting the anodes of the capacitorelement to other components of a device, such as an implantable medicaldevice. In some embodiments, a conductive ribbon 1146 is used to couplethe rolled tabs together.

This application is intended to cover adaptations or variations of thepresent subject matter. It is to be understood that the abovedescription is intended to be illustrative and not restrictive. Thescope of the present subject matter should be determined with referenceto the appended claims, along with the full scope of legal equivalentsto which such claims are entitled.

What is claimed is:
 1. An apparatus comprising: a first electrode; asecond electrode stacked with the first electrode; an interconnectadapted to fold upon itself to couple the first electrode to the secondelectrode, wherein the first electrode, the second electrode and theinterconnect include a unitary substrate; a sintered material disposedon the unitary substrate; a third electrode stacked between the firstand second electrodes; and a case enclosing the first electrode, thesecond electrode, the third electrode and the interconnect.
 2. Theapparatus of claim 1, wherein the first electrode includes a first tab,and wherein the second electrode includes a second tab coupled to thefirst tab.
 3. The apparatus of claim 2, comprising a first clip adaptedto couple the first tab with the second tab.
 4. The apparatus of claim2, comprising a first clip coupled to the first tab and a second clipcoupled to the second tab, wherein the first clip is coupled to thesecond clip.
 5. The apparatus of claim 1, wherein the first electrodeincludes a first tab extending from a first location along a perimeterof the first electrode, the first tab including a first connectionportion, and wherein the first electrode includes a second tab extendingfrom a second location along the perimeter of the first electrode, thesecond tab coupled to the second electrode.
 6. The apparatus of claim 5,wherein the second tab includes a second connection portion, the firstconnection portion is coupled to the second connection portion, thefirst connection portion and the second connection portion aresubstantially free of sintered material.
 7. The apparatus of claim 5,including a clip physically and electrically coupling the first tab andthe second tab.
 8. The apparatus of claim 5, including: a first clipcoupled to the first tab; a second clip coupled to the second tab; and aweld coupling the first clip and the second clip.
 9. The apparatus ofclaim 1, including a case connection tab coupling the first and secondelectrode to the case.
 10. The apparatus of claim 1, comprising afeedthrough and a ribbon coupling the first and second electrodes to thefeedthrough.
 11. The apparatus of claim 1, including additionalelectrodes, the additional electrodes stacked with the first and secondelectrodes, wherein the additional electrodes each include a respectiveinterconnect of a plurality of interconnects, the plurality ofinterconnects folded together and electrically coupled with one another.12. The apparatus of claim 11, including a ribbon physically andelectrically coupling the plurality of interconnects.
 13. The apparatusof claim 12, wherein the ribbon is coupled to the case.
 14. Theapparatus of claim 12, including a feedthrough coupled to the case,wherein the ribbon is coupled to the feedthrough, and the feedthroughelectrically insulates the ribbon from the case.
 15. The apparatus ofclaim 1, wherein the unitary substrate is a foil that is solid andmonolithic.
 16. A method, comprising: sintering a first material onto afirst substrate portion of a unitary substrate to form a firstelectrode; sintering a second material onto a second substrate portionof the unitary substrate to form a second electrode; folding aninterconnect of the first substrate upon itself, wherein the firstelectrode and stacking the first electrode onto the second electrode;stacking a third electrode between the first and second electrodes; andenclosing the first electrode, the second electrode, the third electrodeand the interconnect in a case.
 17. The method of claim 16, comprisingforming a first tab out of material from a portion of the firstsubstrate, and forming a second tab out of material from the secondsubstrate.
 18. The method of claim 17, comprising clipping the first taband the second tab with a clip.
 19. The method of claim 17, comprisingclipping a first clip to the first tab; clipping a second clip to thesecond tab; and coupling the first clip and the second clip.
 20. Themethod of claim 19, comprising welding the first clip to the secondclip.